1. Field of the Invention
The invention is directed to a device for applying mechanical tension to a tape placed into a cartridge, particularly a fast-running tape, which is to be unwound from a first reel and is to be wound onto a second reel, wherein the reels lie on respective reel hubs and wherein the tape is guided around at least two guide rollers, between which the tape runs essentially in a straight line wherein the reels are driven by an internal belt.
2. Description of the Prior Art
The mechanical tension of a tape, particularly of a magnetic tape, is of important for maintaining good contact of the magnetic tape with a write/read head. Good contact is guaranteed given a high tension, whereas it is possible that the tape will flutter over the head given a low tension. Irregularities on the tape can also be the cause of a lift-off of the tape from the head. Relatively low tape tensions particularly occur when the tape is stopped and placed back into motion. The tape must then run for a certain time until the required tension for contact with the head is again built up. Additionally, the tape tension always drastically drops when the running direction is changed.
The difficulties are further intensified when the linear tape density, i.e. the number of bit transitions per mm, is increased. A high density results in an increased signal loss when the exact write or read position is not observed. Since the losses for a given distance between the tape and the head exponentially rise with the wavelength of the signal, the problem of lift-off of the tape from the head becomes more critical as the signal density increases.
In general, a high tape tension can contribute to producing the required, good tape-to-head contact, even when there are slight tape irregularities.
In conventional cartridges, the mechanical tension is generated for the tape by a belt that, inside the cartridge, runs along the tape wound onto reels. The belt is driven from the exterior of the cartridge and thereby in turn moves the tape; the motion of the tape then builds up the tape tension. This basic principle for building a mechanical tension on the tape has been followed unmodified for nearly 20 years. Although it would be possible to increase the tape tension in such cartridges so that a higher friction is generated at rollers around which the belt is guided (preferably at the rollers that are arranged in the corners of the cartridge), an increased friction at these rollers requires a higher torque that must be exerted in order to move the overall arrangement. This requires that a more powerful motor be provided, and thus a larger motor as a rule. Additionally, far more heat is dissipated. This approach would also have the disadvantages that the difference in the respective stiffnesses of the tape and belt would be more pronounced, and thus undefined conditions would initially prevail after the tape is started until a stable tape tension has been achieved in an equilibrium condition.
The aforementioned problems are further intensified in fast-running tapes, i.e. particularly given applications in streamers.